The present invention relates generally to overvoltage protection and, more particularly, to a system and method to protect an integrated circuit from overvoltage conditions.
Numerous types of electronic devices for a myriad of applications employ electrical circuits implemented as one or more integrated circuits (ICs). For example, ICs are configured to achieve desired functions, for example, control of associated devices, digital-to-analog (D/A) or analog-to-digital (A/D) conversion, mixed signal analysis, etc.
Typically, an integrated circuit is designed to tolerate a specified maximum operating power supply voltage. The maximum voltage is usually higher than the nominal operating voltage by about 10% or less. Under some transient conditions, however, the voltages that can appear on the supply pins of the IC are much greater than this maximum operating voltage, known as an overvoltage condition. An overvoltage condition can cause damage to the IC, such as if voltage applied to one or more associated components exceeds the breakdown voltage of such components. For example, IC components of a power driver, such as are used to modulate large currents necessary to drive mechanical devices (e.g., motors), are susceptible to damage due to overvoltage conditions.
One solution is to employ a shunt regulator to limit the voltage during an overvoltage condition. However, a shunt regulator usually requires a large device to handle high current and provide desired high power dissipation. Such a device tends to require a large amount of die area on the IC. It also has been determined that transients can damage the shunt regulator itself, which damage can, in turn, cause damage to the IC.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates generally to overvoltage protection. One aspect of the present invention provides a protection system for an integrated circuit, such as can be configured to control operation of one or more motors. The integrated circuit includes an input terminal that receives an input supply voltage. A detection system detects an overvoltage condition at the input terminal or at other parts of the integrated circuit and provides an overvoltage condition signal to indicate a condition in which overvoltage protection may be desired. In response to the overvoltage condition signal, one or more variable resistance devices in the system, such as power devices of associated driver circuitry, are controlled to limit the voltage across such devices. For example, where the variable resistance devices are power transistors, such transistors can be turned on by associated controls to limit the voltage across the transistors. This can effectively increase the input voltage at which breakdown of the transistors usually occurs.
In accordance with a particular aspect, the overvoltage protection system can include a driver having at least one pair of high-side and low-side power devices electrically coupled in series between the input terminal and ground potential. A node interconnecting the pair of power devices can be coupled to a terminal that is operative to provide power to an associated phase of a motor, such as spindle motor, a voice coil motor, or other motor system. To help protect each of the power devices in circumstances of an overvoltage condition, an overvoltage control system can be connected to each of the high-side and low-side power devices to control each of the respective devices in a mode more tolerant to an overvoltage condition. Such control can be based on the overvoltage condition signal as well as a voltage potential across the respective high-side and low-side power devices.
Another aspect of the present invention provides a method to protect an integrated circuit. The method, which can be implemented relative to a driver of the integrated circuit, includes detecting a condition in which overvoltage protection is desired. In response to detecting the condition, at least one of the first and second active devices (e.g., power transistors of the driver) are operated in a mode that limits a voltage potential across the respective power devices so as to be more tolerant to the detected overvoltage condition.
The following description and the annexed drawings set forth certain illustrative aspects of the invention. These aspects are indicative, however, of a few ways in which the principles of the invention may be employed. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.